We propose to characterize longevity assurance genes (LAGs) through global gene expression profiling of a panel of recombinant inbred (RI) nematode and mouse strains of varying life expectancy, as well as long-lived mutant nematode strains. Our experimental design--which derives power from its comparative nature--aims to identify those genes (a) for which transcriptional level is consistently associated with long lifespan across RI lines and in mutant versus wild-type animals, and (b) for which such associations are found independently in multiple species. This experimental approach will require coordinated efforts in organismal biology, genetics, genomics, and statistics, and the team members assembled reflect this diversity. Our specific aims are: 1. To quantitatively characterize the lifespans of twelve nematode RI lines in two species. Mean and maximum lifespans will be confirmed for six existing RI lines of C. elegans and six newly-isolated RI lines of C. briggsae; 2. To test the hypothesis that whole-genome comparative expression analysis of RI lines and mutant strains of C. elegans will identify LAG candidates. Whole-genome microarray analysis of gene expression in six RI lines and two mutant strains of C. elegans will be carried out, at fixed chronological and physiological ages. We will employ highly sensitive Q-PCR analysis to validate the expression levels of candidate genes picked from microarray analysis; 3. To determine which of the candidate genes characterized in Specific Aim 2 are necessary LAGs. The use of RNAi technology to manipulate the expression of a subset of candidate genes discovered in Specific Aim 2 in C. elegans will permit a relative weight to be assigned to these genes; 4. To identify LAG candidates in recombinant inbred lines of C. briggsae via transcriptional profiling. This specific aim will (a) allow us to characterize "private" versus "public" mechanisms for increasing life expectancy, and (b) permit an independent set of data to support (or contradict) those data generated with the use of RNAi in Specific Aim 3. 5. To extend the analytical approach to mouse RI lines. In years four and five we will apply the functional genomic approach defined above, as well as statistical methods refined during the first three years, to the analysis of mouse RI lines with differential lifespans.